The research objective is to continue to evaluate microwave thermography as a means of sensing subcutaneous temperatures in humans in a non-invasive manner. This harmless, painless, technique sends no radiation into the body. Like infrared thermography, it measures the natural thermal radiation by body tissue. It differs from infrared thermography in detection of thermal abnormalities because it senses tissue temperature at depths of several cm. With N.I.G.M.S. support we have conducted clinical trials for breast cancer detection with a 3.3. GHz instrument, with over 2000 women; 26 had breast cancer proven by biopsy. The resulting true positive and true negative rates exceed 70 percent, and are comparable to the infrared rates. The microwave and infrared techniques together detected 96 percent of the cancers. We propose to conduct similar studies at 1.3 and 6.0 GHz to determine the best frequency for microwave detection of breast cancer. We will carry out clinical detection studies of other diseases, including cerebrovascular disease, peripheral vascular disease, and tumors in internal organs. Improvements in antenna resolution, scanning and imaging, and thermal pattern analysis will be carried out.